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Diffstat (limited to 'Eigen/src/IterativeLinearSolvers/BiCGSTAB.h')
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diff --git a/Eigen/src/IterativeLinearSolvers/BiCGSTAB.h b/Eigen/src/IterativeLinearSolvers/BiCGSTAB.h new file mode 100644 index 000000000..126341be8 --- /dev/null +++ b/Eigen/src/IterativeLinearSolvers/BiCGSTAB.h @@ -0,0 +1,254 @@ +// This file is part of Eigen, a lightweight C++ template library +// for linear algebra. +// +// Copyright (C) 2011 Gael Guennebaud <gael.guennebaud@inria.fr> +// Copyright (C) 2012 Désiré Nuentsa-Wakam <desire.nuentsa_wakam@inria.fr> +// +// This Source Code Form is subject to the terms of the Mozilla +// Public License v. 2.0. If a copy of the MPL was not distributed +// with this file, You can obtain one at http://mozilla.org/MPL/2.0/. + +#ifndef EIGEN_BICGSTAB_H +#define EIGEN_BICGSTAB_H + +namespace Eigen { + +namespace internal { + +/** \internal Low-level bi conjugate gradient stabilized algorithm + * \param mat The matrix A + * \param rhs The right hand side vector b + * \param x On input and initial solution, on output the computed solution. + * \param precond A preconditioner being able to efficiently solve for an + * approximation of Ax=b (regardless of b) + * \param iters On input the max number of iteration, on output the number of performed iterations. + * \param tol_error On input the tolerance error, on output an estimation of the relative error. + * \return false in the case of numerical issue, for example a break down of BiCGSTAB. + */ +template<typename MatrixType, typename Rhs, typename Dest, typename Preconditioner> +bool bicgstab(const MatrixType& mat, const Rhs& rhs, Dest& x, + const Preconditioner& precond, int& iters, + typename Dest::RealScalar& tol_error) +{ + using std::sqrt; + using std::abs; + typedef typename Dest::RealScalar RealScalar; + typedef typename Dest::Scalar Scalar; + typedef Matrix<Scalar,Dynamic,1> VectorType; + RealScalar tol = tol_error; + int maxIters = iters; + + int n = mat.cols(); + VectorType r = rhs - mat * x; + VectorType r0 = r; + + RealScalar r0_sqnorm = r0.squaredNorm(); + Scalar rho = 1; + Scalar alpha = 1; + Scalar w = 1; + + VectorType v = VectorType::Zero(n), p = VectorType::Zero(n); + VectorType y(n), z(n); + VectorType kt(n), ks(n); + + VectorType s(n), t(n); + + RealScalar tol2 = tol*tol; + int i = 0; + + while ( r.squaredNorm()/r0_sqnorm > tol2 && i<maxIters ) + { + Scalar rho_old = rho; + + rho = r0.dot(r); + if (rho == Scalar(0)) return false; /* New search directions cannot be found */ + Scalar beta = (rho/rho_old) * (alpha / w); + p = r + beta * (p - w * v); + + y = precond.solve(p); + + v.noalias() = mat * y; + + alpha = rho / r0.dot(v); + s = r - alpha * v; + + z = precond.solve(s); + t.noalias() = mat * z; + + w = t.dot(s) / t.squaredNorm(); + x += alpha * y + w * z; + r = s - w * t; + ++i; + } + tol_error = sqrt(r.squaredNorm()/r0_sqnorm); + iters = i; + return true; +} + +} + +template< typename _MatrixType, + typename _Preconditioner = DiagonalPreconditioner<typename _MatrixType::Scalar> > +class BiCGSTAB; + +namespace internal { + +template< typename _MatrixType, typename _Preconditioner> +struct traits<BiCGSTAB<_MatrixType,_Preconditioner> > +{ + typedef _MatrixType MatrixType; + typedef _Preconditioner Preconditioner; +}; + +} + +/** \ingroup IterativeLinearSolvers_Module + * \brief A bi conjugate gradient stabilized solver for sparse square problems + * + * This class allows to solve for A.x = b sparse linear problems using a bi conjugate gradient + * stabilized algorithm. The vectors x and b can be either dense or sparse. + * + * \tparam _MatrixType the type of the sparse matrix A, can be a dense or a sparse matrix. + * \tparam _Preconditioner the type of the preconditioner. Default is DiagonalPreconditioner + * + * The maximal number of iterations and tolerance value can be controlled via the setMaxIterations() + * and setTolerance() methods. The defaults are the size of the problem for the maximal number of iterations + * and NumTraits<Scalar>::epsilon() for the tolerance. + * + * This class can be used as the direct solver classes. Here is a typical usage example: + * \code + * int n = 10000; + * VectorXd x(n), b(n); + * SparseMatrix<double> A(n,n); + * // fill A and b + * BiCGSTAB<SparseMatrix<double> > solver; + * solver(A); + * x = solver.solve(b); + * std::cout << "#iterations: " << solver.iterations() << std::endl; + * std::cout << "estimated error: " << solver.error() << std::endl; + * // update b, and solve again + * x = solver.solve(b); + * \endcode + * + * By default the iterations start with x=0 as an initial guess of the solution. + * One can control the start using the solveWithGuess() method. Here is a step by + * step execution example starting with a random guess and printing the evolution + * of the estimated error: + * * \code + * x = VectorXd::Random(n); + * solver.setMaxIterations(1); + * int i = 0; + * do { + * x = solver.solveWithGuess(b,x); + * std::cout << i << " : " << solver.error() << std::endl; + * ++i; + * } while (solver.info()!=Success && i<100); + * \endcode + * Note that such a step by step excution is slightly slower. + * + * \sa class SimplicialCholesky, DiagonalPreconditioner, IdentityPreconditioner + */ +template< typename _MatrixType, typename _Preconditioner> +class BiCGSTAB : public IterativeSolverBase<BiCGSTAB<_MatrixType,_Preconditioner> > +{ + typedef IterativeSolverBase<BiCGSTAB> Base; + using Base::mp_matrix; + using Base::m_error; + using Base::m_iterations; + using Base::m_info; + using Base::m_isInitialized; +public: + typedef _MatrixType MatrixType; + typedef typename MatrixType::Scalar Scalar; + typedef typename MatrixType::Index Index; + typedef typename MatrixType::RealScalar RealScalar; + typedef _Preconditioner Preconditioner; + +public: + + /** Default constructor. */ + BiCGSTAB() : Base() {} + + /** Initialize the solver with matrix \a A for further \c Ax=b solving. + * + * This constructor is a shortcut for the default constructor followed + * by a call to compute(). + * + * \warning this class stores a reference to the matrix A as well as some + * precomputed values that depend on it. Therefore, if \a A is changed + * this class becomes invalid. Call compute() to update it with the new + * matrix A, or modify a copy of A. + */ + BiCGSTAB(const MatrixType& A) : Base(A) {} + + ~BiCGSTAB() {} + + /** \returns the solution x of \f$ A x = b \f$ using the current decomposition of A + * \a x0 as an initial solution. + * + * \sa compute() + */ + template<typename Rhs,typename Guess> + inline const internal::solve_retval_with_guess<BiCGSTAB, Rhs, Guess> + solveWithGuess(const MatrixBase<Rhs>& b, const Guess& x0) const + { + eigen_assert(m_isInitialized && "BiCGSTAB is not initialized."); + eigen_assert(Base::rows()==b.rows() + && "BiCGSTAB::solve(): invalid number of rows of the right hand side matrix b"); + return internal::solve_retval_with_guess + <BiCGSTAB, Rhs, Guess>(*this, b.derived(), x0); + } + + /** \internal */ + template<typename Rhs,typename Dest> + void _solveWithGuess(const Rhs& b, Dest& x) const + { + bool failed = false; + for(int j=0; j<b.cols(); ++j) + { + m_iterations = Base::maxIterations(); + m_error = Base::m_tolerance; + + typename Dest::ColXpr xj(x,j); + if(!internal::bicgstab(*mp_matrix, b.col(j), xj, Base::m_preconditioner, m_iterations, m_error)) + failed = true; + } + m_info = failed ? NumericalIssue + : m_error <= Base::m_tolerance ? Success + : NoConvergence; + m_isInitialized = true; + } + + /** \internal */ + template<typename Rhs,typename Dest> + void _solve(const Rhs& b, Dest& x) const + { + x.setZero(); + _solveWithGuess(b,x); + } + +protected: + +}; + + +namespace internal { + + template<typename _MatrixType, typename _Preconditioner, typename Rhs> +struct solve_retval<BiCGSTAB<_MatrixType, _Preconditioner>, Rhs> + : solve_retval_base<BiCGSTAB<_MatrixType, _Preconditioner>, Rhs> +{ + typedef BiCGSTAB<_MatrixType, _Preconditioner> Dec; + EIGEN_MAKE_SOLVE_HELPERS(Dec,Rhs) + + template<typename Dest> void evalTo(Dest& dst) const + { + dec()._solve(rhs(),dst); + } +}; + +} // end namespace internal + +} // end namespace Eigen + +#endif // EIGEN_BICGSTAB_H |